Several experts told PBS News Hour that it was unlikely that sonar was involved in the tragedy.

So what accounts for this year’s high numbers?

It’s a question that researchers are trying to answer.

Michael Booth, a Communications Officer at IFAW informed this reporter in an email that research is ongoing.

“The one constant thread among all mass stranding is that like humans, common dolphins involved are highly social animals that depend upon the safety and resources of the group in order to survive,” Booth wrote. “This group mentality that is so helpful to these animals at sea can unfortunately cause otherwise healthy animals to strand en mass when they are near shore. When one animal enters shallow water or strands, the entire group may follow.”

One factor that likely played a role, Booth wrote, is that the waters in the area were unseasonably warm. The dolphins that did strand appeared healthy and likely stranded due to natural events, rather than human causes.

Topography may also play a part. The area has complex inlets and hook-shaped areas, Booth wrote.

While Cape Cod’s topography may have played a part, it doesn’t account for the drastic increase in numbers.

The tragedy is even greater in Peru. Possibly as many as 2800 dolphins have stranded along a 137 mile stretch of the north coast. Again, most were common dolphins.

Twenty-four dolphins washed up on Jan. 21st, in Piura, in Northern Peru, near the border of Ecuador. More than 870 were spotted in February and March on the beaches in the Lambayeque region, south of Piura. Another 1500 were reported by the staff of a coastal reserve in the same area on March 10th, and on March 21st 416 washed up in Piura, according to Environmental Health News.

An acoustical impact from testing for oil or a virus or pathogen may have caused the tragedy, the site reported.

Oil exploration near Peru’s coast in this area is ongoing, but it isn’t known whether tests were being conducted when the animals stranded.

Air guns can damage the ears and organs of marine mammals, said Michael Jasny, Senior Policy Analyst at the Natural Resources Defense Council. Sounds from these guns can alter the animal’s dive patterns, he said.

Dolphins also suffer decompression sickness, known as “the bends.”

Disoriented by the noise, they may beach themselves, Jasny said.

“Lots of sound in the wrong place, at the wrong time can lead to mass stranding,” Jasny told Environmental Health News.

The endless search for oil may send countless species into extinction.

It’s also not known if the United States Navy is using sonar to conduct military exercises off of Peru’s coast, Environmental Health News reports.

The public should have the right to know where and when oil companies and the U.S. Navy are conducting these tests.

Sonar systems produce sound waves that sweep the ocean like a floodlight, revealing objects in their path.

Sonar sound waves travel for hundreds of miles. Even 300 miles away from the source, they can be as loud as 140 decibels, which is 100 times more intense than the level known to alter the behavior of large whales, NRDC reports.

The Navy’s most frequently used sonar systems operate in the mid-frequency range.

In 2000, four species of beaked whales stranded on beaches in the Bahamas. The Navy denied any wrongdoing, but an investigation by the government demonstrated that mid-frequency sonar caused the stranding.

Cuvier’s beaked whales in the area nearly vanished. Researchers concluded that the animals either abandoned their habitat or died at sea, NRDC reports.

Mass stranding has also occurred in the Canary Islands, Greece, Madeira, the U.S. Virgin Islands, Hawaii, and other places around the world.

In these cases, whales have suffered bleeding around the brain, the ears, and other tissues, and bubbles in their organs.

The blasts may alter their dive patterns, causing debilitating and fatal injuries, scientists said, according to the NRDC.

With so many animals teetering on the edge of extinction, this is a dangerous game.

Dr. Carlos Yaipen, a marine environmentalist and local veterinarian, examined 20 of the dolphins that washed up in Peru, according to Environmental Health News.

Each animal suffered inner ear hemorrhages and broken ear bones. They also suffered lung lesions and had bubbles in the bloodstream.

He believes an enormous acoustic impact caused injuries.

Some experts are skeptical about this.

Pollutants such as DDT, dioxins, and PCBs can suppress an animal’s immune system, making them vulnerable to stress from noise or climate change and diseases such as leptospirosis, brucellosis, or distemper, Peter Ross told Environmental Health News.

Ross is a research scientist at the Institute of Ocean Sciences in British Columbia.

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